Process for preparing 1, 1, 1-trifluoro-2-bromoethane



Nneo TNT omen STATES PROCESS FOR PREPARING LLl-TRI- FLUORO-Z-BROMOETHANE Edmund B. Towne and Joseph B. Dickey, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application October 24, 1947, Serial No. 782,028

This invention relates to an improved process for preparing 1,1,1-trifiuoro-2-bromoethane and more particularly to the preparation of this compound by the fiuorination of 1,1-dichloro-L2- dibromoethane. 5

,l-trifluuro-2-bromoethane was first premoethane can be obtained by heating 1,1-dipared by Swarts, Compt. rend. 197, 1261 (1933), chlorol,2-dibromoethane in an autoclave with y a method which involved in addition to other hydrogen fluoride and antimony trifluoride in the steps the reduction with platinum oxide of tripresence of antimony pentachloride a at fiuoroacetic acid to trifiuoroethanol and subse- 1o lyst. That hydrogen fluoride is an essential in; quent bromination of this compound using phOS- gradient of the reaction mixture is apparent phorous pentabromide to yield the desired comfrom the fact that when this compound was pound. Obviously this method is costly and omitted only CCl2FCH2Br and CCIFzCI-IzBr re-i roundabout and therefore unsuited for commersulted from the process. That antimony trifluoe cial application. Henne and Renoll, J. Am. ride is likewise necessary was also determined by Chem. Soc. 58, 887 (1936), prepared CFsCHeBI' omitting it. Here again only CClzFCI-IzBl and in very poor yield and in an impure state by re- CCIFzCI-IzBl were obtained. f acting CI-IBmCHBrz with SbFsClz. More recently The following examples illustrate the manner and since our work was completed CF3CI-I2Br of carrying out the process of our invention. has been prepared in good yields by reacting Emmple 1 CCl-2BrCI-I2Br with a mixture of mercuric oxide and hydrogen fluoride under pressure,. Ind. Eng. 588 grams of CClzBrCHzBI, 448 grams of anti- Chem. 39, 411 (1947). However mercuric comm ny trifluorid and 0 c of im ny r ntapounds are expensive and dangerous to work loride were placed in an autoclave, cooled to" with, elaborate safety precautions being required 5 5 C. There was then added 40 ms of an in their commercial usage. Further, the high y u liquid hydrogen fluoride cooled to '78, expense of the catalyst necessitates additional C. The autoclavewas sealed and the reaction, equipment for recovering and reconverting the miXture at d to 160 C. without shaking durmercuric residue to a usable form. Therefore, in 2 h urs and maintain d at this emperature this process is unsound from a commercialstandfor from one to two u s more, following wh h point. it was cooled to 0 C. There was considerable Known methods for t preparation of pressure in the autoclave and the discharge valvel CFsCI-IzCl were investigated in our efiorts to dewa opened o vent the formed gases u h vise a satisfactory process for preparing Water Scrubber leading o a ry-Ice condenser. CF3CH2BY w th process of U. t t The temperature of the autoclave was allowed to 2, 230,925 (treatment of CClsCI-IzCl with SbFs, increase to d e wh h tim 22 grams s p c and HF) was applied t CBraCI-hBr of low-boiling material were collected in the Dryonly traces of CF3CH2Br could be isolated. Like- Ice receiver- At this p nt he autoclave was wise when CCl2BrCHzBr was treated in accordagain Sealed and the reaction mixture ance with this process negligible amounts of the heated to and maintained at this emperl desired trifiuoro compound were form d ature for seven hours. The reaction mixture was. We have found that when CC13CH2C1is mixed then cooled to and e o s ssed with SbFe and a catalytic amount of SbCls and through a Water scrubber to remove hydrogen. h t d in an autoclave t 125 an 3 yield fluoride. The reaction product, CF3CI-I2Br, was of CFsCHzCl can be bt However, when collected in a Dry-Ice receiver, connected to the t process was employed using CClZBrCHZBr as water scrubber, as the autoclave gradually came t ti material less than 2 of CF3CH2B1- up to room temperature. Finally the autoclave. wa btai d, was heated to C. to complete the removal of It is, therefore, an object of this invention to p c The total yield of c ude CFsCI-IrBi'. provide new n improved prgcess f r t 50 was 318 grams or of the theoretical yieldpreparation of 1,1,1etrifiuoro-2-bromoe thane. based on CCl2BrCH2Br. This was washed with It is a further object of this invention to prodilut sodi m i ar na s luti n. d i d. vide a process for the preparation of l,'1,1-tri and fractionally distilled. The yield of pure; fluoro-Z-bromoethane whichis in essence simple CF3CH2B! boiling at 2627 C. was 247 grams and inexpensive. Another object of this invene is.

10 Claims. (Cl. 260-4553) 2 tion is to provide a process which will place the preparation of this important chemical intermediate on a commercially feasible basis. Other. objects will appear hereinafter. I

We have discovered that 1,1,1-trifluoro-2-bro- (66%) The higher boiling residue consisting of;

a mixture of CClF2Cl-I2Br and CF3CHzBr weighed 20 grams.

Example 2 490 grams of CClzBrCHzBr, 448 grams of antimony trifluoride, 12.5 cc. of antimony pentai'luoride, and 435 grams of hydrogen fluoride were charged into an autoclave, cooled to 5 C. The autoclave was sealed and heated gradually to 145 C. over a period of from one to two hours. The reaction mixture was then cooled to C. and the formed gases were vented as in Example 1. The autoclave was sealed again and the reaction mixture was heated to 145 C. and maintained at this temperature for six hours, Whereupon it was cooled to 0 C. The reaction mixture was worked up in accordance with the procedure described in Example 1. The yield of crude CFBCHZBI was 257 grams (82.5%) and of purified CFaCHzBl' 202 grams (65%).

Example 3 588 grams of CClzBrCI-IzBr, 376 grams of antimony trifluoride, 10 cc. of antimony pentachloride, and 420 grams of hydrogen fluoride were charged into an autoclave, cooled to C. The autoclave was sealed and the reaction mixture was heated gradually to 165 C. over a period of from one to two hours. The reaction mixture was then cooled to 0 C. and the formed gases were vented as in Example 1. The autoclave was sealed again and the reaction mixture was heated to 150 C. and maintained at this temperature for nine hours, whereupon it was cooled to 0 C. The reaction mixture was worked up in accordance with the procedure described in Example 1. 274 grams of crude CFsCHzBl were obtained which corresponds to a theoretical yield based on CClzBICHzBr of 73%. When purified the yield was 214 grams (57%).

Example 4 512 grams of CClzBlCHZBI, 394 grams of antimony trifluoride, 8 co. of antimony pentachloride, and 620 grams of hydrogen fluoride were charged into an autoclave, cooled to 5 C. The autoclave was sealed and the reaction mixture was heated gradually over a period of about one hour to 155 C. and maintained at this temperature for thirty hours. The reaction mixture was then cooled to 0 C. and worked up in accordance with the procedure described in Example 1. The yield of crude CFaCHcBr was 179 grams (55%) and of purified product 150 grams (46%).

While CF3CH2B1' can be prepared by heatin CClzBrCHzBI with a mixture of antimony trifluoride, antimony pentachloride and hydrogen fluoride in accordance with the directions given herein without the cooling and venting steps greatly improved results are obtained when the reaction mixture is cooled below the boiling point of hydrogen fluoride and the first fonned gaseous reaction products (principally hydrogen chloride with some hydrogen bromide) are vented. Accordingly, it is advantageous in carrying out the process of our invention to employ the cooling and venting operations just referred to and this represents the preferred form of our invention.

As illustrated in Example 4,. when the venting step is omitted, a heating period up to thirty hours is insumcient to produce as high a yield as is obtained when heating periods of six to ten hours are used with venting incorporated in the process. When heating periods on the order of ten to fifteen hours at 140-161? C. are used without venting, the principal products obtained are 75 of azo compounds of use for the dyeing or colora 4 CClzFCHzBr and CClFzCI-IzBl with little or no CFaCHzBl. Therefore, a tremendous saving in time and increase in yield result from the discovery of the venting procedure. This probably means that the first step of the reaction is partial fluorination of CClzBrCrlzBr to produce CClFzCHzBI. This is followed by the splitting out of HCl and HBr leaving an unsaturated intermediate (probably CF2=CHB1) to which hydrogen fluoride then adds.

The composition of the fluorinating mixture may be varied Within reasonable limits without appreciably affecting the yield of CF.CH2Br. In our process 1,1-dichloro-1,2-dibromoethane and antimony trifluoride are ordinarily employed in approximately equimolar amounts. However, a molar reduction up to 20% in the amount of antimony trifluoride used does not effect any substantial decrease in yield. Similarly, more than one mole proportion of antimony trifluoride can be used but is not necessary. In general, 0.7 to 1.5 mole proportion of antimony trifluoride is used. The amount of hydrogen fluoride used may also be varied considerably. While in our experiments We have successfully used as high as 15.5 mole proportionsof hydrogen fluoride it is not necessary to use such high amounts. The use of 6 to 9 mole proportions appears to be advantageous although less than 6 and more than 15 mole proportions of hydrogen fluoride, for example, can be used. Antimony pentachloride is used in small, catalytic amounts, such as 0.025 to 0.05 mole proportions. While the proportions indicated are those that would normally be used, it will be understood that 1,1,1-trifiuoro-2-bromoethane can be obtained even if these proportions are varied somewhat. Mole proportions are with respect to the amount of CClzBICI-IzBl used.

The reaction temperature at which we prefer to carry out the fluorination of CC12B1CH2B1 is between and C. It will be understood, however, that this preference constitutes no limitation upon the process of our invention as temperatures from 130 to C., for example, can be used. The upper limit of temperatures is the point at which decomposition of the reactants be-' gins to occur to an appreciable extent.

The order and manner of addition of starting materials is immaterial to the success of the reaction. We have found that the simplest and most convenient method is to place in the autoclave the calculated quantities of CC12B1CH2BI, SbFa and SbCl5 and then cool the whole in an ice-salt mixture to about 0 C. Anhydrous liquid hydrogen fluoride which has been previously cooled to approximately 78 C. is then added.

While we have disclosed the carrying out of our process in an autoclave it is to be clearly understood that any suitable closed reaction vessel can be employed whether termed an autoclave or not.

A large part of the value of our process lies in the utility of the compound 1, ,1-trifluoro-2- bromoethane. It can be adapted for use as a solvent or an intermediate in the preparation of larger molecules. Probably its most important use is in the latter connection. The advantage of this compound over the compound CFbCHzCl in alkylation reactions stems from the greater reactivity of the bromine atom over the corresponding chlorine atom. Therefore, the radical CFsCHz-" may be introduced into organic molecules with greater ease than when this is accomplished by using the corresponding chloro compound.

Coupling components useful in the preparation tion of cellulose acetate textile materials can be prepared by reacting an aminobenzene compound such as, for example, aniline, m-chloroaniline and m-toluidine with 1,1,1-trifiuoro-2-bromoethane in the presence of an acid binding agent such as, for example, sodium carbonate, potassium carbonate, sodium hydroxide and sodium bicarbonate. These coupling components when coupled with diazotized aromatic amines such as p-nitroaniline, o-chloro-p-nitroaniline, 2,6-dichloro-4- nitroaniline and Z-bromo-6-chloro-4-nitroaniline, for example, yield valuable dyes for the coloration of cellulose acetate textile materials. Azo conipounds of the character just indicated are described and claimed in Dickey application Serial No. 631,469, filed November 28, 1945. The preparation of these compounds is indicated hereinafter.

1 Example A.N-(2,2,2-trifluoroethyl) aniline 17 grams of l,1,1-trifiuoro-2-bromoethane, 9.3 grams of aniline and 6 grams of sodium carbonate are placed in a suitable reaction vessel and heated under refluxing conditions until carbon dioxide ceases to be evolved. Upon cooling, the reaction mixture is extracted with ethyl alcohol and the ethyl alcohol extract is fractionated under reduced pressure (2 mm., for example) to give a good yield of N- (2,2,2-trifiuoroethyl) aniline which is a colorless liquid boiling at 84 C.-85 C./ 15 mm. and which has a refractive index of n 1.4818.

By the substitution of 12.8 grams of m-chloroaniline, and 10.7 grams of m-toluidine for aniline in the foregoing example, N-(2,2,2-trifiuoroethyl) -m-chloroaniline and N-(2,2,2-trifluoroethyl) -m-toluidine, respectively, are obtained.

Example B.-N-fi-hydro:ryethyl-N- (2,2,2-trifluoroethyl) aniline 17 grams of N-(2,2,2-trifiuoroethyl)aniline, grams of ethylene oxide and 50 cc. of dioxane are heated together with stirring in an autoclave at 180 C. for six hours. Upon cooling, the reaction mixture is removed from the autoclave and distilled under reduced pressure. N-B-hydroxyethyl-N-( ,2,2-trifiuoroethyl) aniline boiling at 102 C.-103 C./1.5 mm. is obtained.

By the use of 20.9 grams of N-(2,2,2-trifiuoroethyl) -m-chloroaniline in place of the N-(2,2,2- trifluoroethyl) aniline in the foregoing example a good yield of N-fi-hydroxyethyl-N-(2,2,2-trifiuoroethyl)-m-chloroaniline is obtained, Similarly, if 18.9 grams of N 2,2,2-triiiuoroethyl) -mtoluidine are used in the foregoing example a good yield of N-c-hydroxyethyl-N-(2,2,2-trifluoroethyl) -m-toluidine is obtained.

Example C. 1-(4-nitrophenylaeo-4-(N-B-hydroryethyl) -N-2,2,2-trifluoroethyl) -aminoben- CHzCFs CHQCHQOH ually added with stirring. Following the addition of the diazonium solution the mixture resulting is stirred, while maintaining a temperature of 010 0., for about 30 minutes after Which the coupling reaction which takes place is completed by neutralizing the hydrochloric acid with sodium acetate. The dye compound formed is recovered by filtration, washed with water and dried. It colors cellulose acetate rayon and nylon red shades.

Example D. 1-(4-nitrophenyZaeo-4-(N-fl-hydroxyethyl) -N-2,2,2-triflu0roethyl) m-chloroaniline 13.8 grams of p-nitroaniline are diazotized and the diazonium compound obtained is coupled with 25.3 grams of N-b-hydroxyethyl-N-(2,2,2-trifluoroethyl) -m-chloroaniline., The diazotization, coupling and dye recovery operations can be carried out in accordance with the procedure described in Example 1. The dye compound obtained colors cellulose acetate rayon and nylon orange shades.

Example E. 1- (2-chloro-4-nitrophenylazo) -2- methz/Z-4-(N-fl-hi/clromyethyZ-N (2,2,2-t7'z'fluomethyl) -aminobenzene 17.3 grams of o-chloro-p-nitroaniline are diazotized and the diazonium compound obtained is coupled with 23.3 grams of N-B-hydroxyethyl-N- (2,2,2-trifiuoroethyl) -m-toluidine. The diazotlzation, coupling and dye recovery operations can be carried out in accordance with the procedure described. in Example 1. The dye compound obtained colors cellulose acetate rayon and nylon rubine shades.

The dye compounds obtained by coupling diazotized p-nitroaniline with N-(2,2,2-trifiuoroethyl) aniline, N (2,2,2-trifluoroethyl) m-chloroaniline and N-(2,2,2-trifluoroethyl) -m-toluidine color cellulose acetate textile materials yellowishorange shades, the shade in the latter case being more orange than in the first two cases.

So far as we are aware the pressure under which our process is carried out is not critical and is subject to considerable variation depending, for example, upon the proportions of the reactants employed, such as the amount of hydrogen fluoride used, the temperature at which the reaction is carried out and the size of the reaction vessel with respect to the amount of reactants employed. The pressures in Examples 1 to 3 prior to venting were of the order of 800- 1000 pounds per square inch and less after venting. In Example 4 the pressure was slightly higher than in Examples 1 to 3. While it is very difficult to set forth limits because of the variables involved our experiments indicate that good results are obtained when the reaction mixture is heated at a temperature of C.190 C., particularly C. C., for 1 to 2 hours prior to venting. The pressures developed under these reaction conditions are substantial as that term is used herein and are normally 200 or more pounds per square inch.

We claim:

1. The process of preparing 1,1,1-trifluoro-2- bromoethane which comprises heating with antimony trifiuoride, hydrogen fluoride and antimony pentachloride in a closed reaction vessel at a temperature below which appreciable decomposition of the reactants occurs and under pressure to form 1,1,l-trifluoro-Z-bromoethane and recovering the 1 ,1,1-trifiucro-i-bromoethane thus formed.

with antimony trifluoride, hydrogen fluoride and antimony pentachloride in a closed reaction vessel at a temperature below which appreciable decomposition of the reactants occurs until a substantial pressure is built up in the reaction vessel, cooling the reaction mixture below the boiling point of hydrogen fluoride and then venting the gases formed during the heating operation above described, again heating the reaction mixture at a temperature below which appreciable decomposition of the reactants occurs until formation of 1,1,i-trifiuoro-fi-bromoethane is complete and recovering the LLI-triiiuoro 2 bromoethane thus formed.

3. The process of preparing 1,1,1-trifiucro-2- bromoethane which comprises heating CCizBrCi-IzBr with antimony trifiuoride, hydrogen fluoride and antimony pentachloride in a closed reaction vessel at a temperature of 140 C.17t C. and under pressure to form 1,1,1-trifiuoro-2-bro1noethane and recovering the 1,1,1-trifiuoro2-bromoethane thus formed.

4. The process of preparing 1,1,1-trifluoro-2- bromoethane which comprises heating with antimony trifluoride, hydrogen fluoride and antimony pentachloride in a closed reaction vessel at a temperature of 140 C.-170 C. until a substantial pressure is built up in the reaction vessel, cooling the reaction mixture below the boiling point of hydrogen fluoride and then venting the gases formed during the heating operation above described, again heating the reaction mixture to a temperature of 140 C.170 C. and maintaining the reaction mixture at this temperature until formation of 1,1,1-trifluoro-2- bromoethane is complete and recovering the 1,1,1-trifluoro-2-bromoethane thus formed.

5. The process of preparing 1,1,1-trifluoro-2- bromoethane which comprises heating CCIzBrCI-IzBr with antimony trifiuoride and hydrogen fluoride in the presence of antimony pentachloride as a catalyst in a closed reaction vessel at a temperature of 140 C.170 C. for 1 to 2 hours, cooling the reaction mixture below the boiling point of hydrogen fluoride and then venting the gases formed during the heating operation above described, again heating the reaction mixture to a temperature of 140 C.-170 C. and maintaining the reaction mixture at this temperature until formation of 1,1,1-trifluoro-2-bromcethane is complete and recovering the 1,1,1-trifluoro-2- brornoethane thus formed.

6. The process of preparing 1,1,1-trifluoro- 2-bromoethane which comprises heating with antimony trifluoride and hydrogen fluoride in the presence of antimony pentachloride as a catalyst in a closed reaction vessel at a temperature of 140 C.-170 C. to form 1,1,1-trifluoro-2- bromoethane and recovering the 1,1,1-trifluoro- 2-b'romoethane thus formed.

l. The process of preparing Li i-trifiuoro fi bromoethane which comprises heating one mole equivalent of CChBI'CI-IzBr with 0.7 to 1.5 vmole proportion of antimony trifiuoride and 6 to 15 mole proportions of hydrogen fluoride in the presence of antimony pentachloride as a catalyst in a closed reaction vessel at a temperature below which appreciable decomposition of the reactants occurs and under pressure to form 1,l,1 trifiuoro- 2-bromoethane and recovering the 1,1,1-trifiuoro-2-bromoethane thus formed.

8, The process of preparing 1,1,1-trifluoro-2- bromoethane which comprises heating one mole equivalent of CClzBrCI-IzBr with 0.7 to 1.5 mole proportion of antimony trifiuoride and 6 to 15 mole proportions of hydrogen fluoride in the presence of antimony pentachloride as a catalyst in a closed reaction vessel at a temperature below which appreciable decomposition of the reactants occurs until a substantial pressure is built up in the reaction vessel, cooling the reaction mixture below the boiling point of hydrogen fluoride and then venting the gases formed during the heating operation above described, again heating the reaction mixture at a temperature below which appreciable decomposition of the reactants occurs until formation of 1,1,1-trifluoro-2-bromoethane is complete and recover ing the 1,1,1-ti'ifluoro-2-bromoethane thus formed.

9. The process of preparing 1,1,1-trifluoro-2- bromoethane which comprises heating one mole equivalent or CClzBrCI-IzBr with 0.7 to 1.5 mole proportion of antimony trifluoride and 6 to 15 mole proportions of hydrogen fluoride in the presence of antimony pentachlcride as a catalyst in a closed reaction vessel at a temperature of C.- C. for 1 to 2 hours, cooling the reaction mixture below the boiling point of hydrogen fluoride and then venting the gases formed during the heating operation above described, again heating the reaction mixture to a temperature of 140 C.-l70 C. and maintaining the reaction mixture at this temperature until formation of 1,1,1-trifluoro-2-bromoethane is complete and recovering the 1,1,l trifiuoro-2 brornoethane thus formed.

10. The process of preparing 1,1,1-trifiuoro-2- bronice'thane which comprises heating CClaBlCHzBr with antimony trifiuoride and hydrogen fluoride in the presence of antimony pentachloride as a catalyst in a closed reaction vessel at a temperature below which appreciable decomposition of the reactants occurs to form 1,1,1-trifiuoio-2- bromoethane and recovering the 1,1,1-trifluoro- 2-bromoethane thus formed.

B. TOWNE. JOSEPH B. DICKEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,024,008 Midgley, Jr., et a1. nos. 10, 1935 2,024,095 Daudt et al Y Dec. 10, 1935 OTHER REFERENCES McBee et a1., Ind, Eng. Chem, vol. 39, 409-412 (1947'); 

1. THE PROCESS OF PREPARING 1,1,1-TRIFLUORO-2BROMOETHANE WHICH COMPRISES HEATING 